| Summary: | <p>Abstract</p> <p>Background</p> <p>The 235delC mutation of <it>GJB2</it> gene is considered as a risk factor for the non-syndromic hearing loss (NSHL), and a significant difference in the frequency and distribution of the 235delC mutation has been described world widely.</p> <p>Methods</p> <p>A systematic review was performed by means of a meta-analysis to evaluate the influence of the 235delC mutation on the risk of NSHL. A literature search in electronic databases using keywords “235delC”, “<it>GJB2</it>” associated with “carrier frequency” was conducted to include all papers from January 1999 to June 2011. A total of 36 papers were included and there contained 13217 cases and 6521 controls derived from Oceania, American, Europe and Asian.</p> <p>Results</p> <p>A remarkable heterogeneity between these studies was observed. The combined results of meta-analysis showed that the 235delC mutant increased the risk of NSHL (<it>OR</it> = 7.9, 95%<it>CI</it> 4.77 ~ 13.11, <it>P</it> <0.00001). Meanwhile, heterogeneity of genetic effect was also observed due to the ethnic specificity and regional disparity. Therefore, the stratified meta-analysis was subsequently conducted and the results indicated that the 235delC mutation was significantly correlated with the risk of NHSL in the East Asian and South-east Asian populations (<it>OR</it> = 12.05, 95%<it>CI</it> 8.33~17.44, <it>P</it> <0.00001), but not significantly in the Oceania and European populations (<it>OR</it> = 10.36, 95%<it>CI</it>: 4.68~22.96, <it>Z</it> = 1.68, <it>P</it> >0.05).</p> <p>Conclusions</p> <p>The 235delC mutation of <it>GJB2</it> gene increased the risk of NHSL in the East Asian and South-east Asian populations, but non-significantly associated with the NSHL susceptibility in Oceania and European populations, suggesting a significant ethnic specificity of this NSHL-associated mutation.</p>
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